It is well accepted that bioresorbable orthopedic implants are always the better choice than permanent foreign-body implants, as long as their bioresorption rates, biomechanical properties and variations in biomechanical properties with respect to the resorption processes are appropriately controlled. Among all bioresorbable orthopedic implants, calcium-based implants (calcium phosphate, calcium sulfate, etc), are perhaps the top choice so far. The conventional methods of forming a hardened (set) bone cement in bone cavity involve creating a bone cavity in advance.
Prior-art cavity creation devices having an inflatable and expandable liquid fluid-filled balloon structure have insufficient “lift”—ability to push back compression-fractured bone (e.g., to restore vertebral body height) under certain circumstances due to the “softness” of the balloon.
Prior-art cavity creation devices having an inflatable and expandable balloon-type structure rely on a high pressure liquid fluid to expand a cavity in bone, which increases various high pressure-related risks in clinical procedures.
Prior-art cavity creation devices having a foldable and extendable (expandable) rigid structure have risks of generating stress-concentrated spots and fresh cracks in the readily fractured bone.
Most prior-art rigid-structure cavity creation devices have a hollow structure under expanded/unfolded condition. Once bone chips/fragments are trapped in such devices during unfolding (expanding) and/or folding (collapsing) procedures, such devices have risks of being unable to be retrieved from the treated site, especially through a minimally invasive percutaneous path. Likewise, in case any pieces/components of the rigid-structure devices break off the structure during procedure, these broken-off pieces/components would be very hard to be retrieved, especially through a minimally invasive percutaneous path.
The inventors of the present application in WO 2006/138398 A2 disclose a non-inflated tool for expanding a bone cavity in which an orthopaedic paste is to be implanted comprising a flexible linear filler and a rod with one end thereof connected to one end of the flexible linear filler, so that the flexible linear filler can be pushed by the rod through a tube into a hole of a bone to expand a bone cavity in the bone. The filler may be a wire, band, or chain. Preferably, the chain comprises a series of beads linked one after another or by a string. Despite the ability of this non-inflated tool to effectively create/expand bone cavity, once the linear filler breaks, it would be very hard to retrieve the broken-loose bodies, especially through a minimally invasive percutaneous path. Another risk for the prior-art non-inflated tool is entanglement of the linear filler, which might happen during feeding (expansion) and/or retrieving procedure. When entanglement happens, it would be very hard for the linear filler to be retrieved, especially through a minimally invasive percutaneous path.
For most prior-art rigid-structure cavity creation devices, an easy, accurate, reliably and safe bone-expansion procedure for a fractured bone is always a great challenge. There is a need in developing an easy, accurate, reliably and safe technique for creating a cavity in a bone, in which an orthopaedic paste is to be implanted.